1. The Field of the Invention
The present invention relates to a clock generator module, and more particularly relates to a modular clock generator circuit providing various clock frequencies required. Thus, one particular electronic product is extendable for satisfying various frequencies requirements without incurring high cost on product design, and manufacturing and product management.
2. Description of the Related Art
The available measuring devices, data acquisition device or equipment, comprise a clock generator circuit for either analog input/output functions or digital input/output functions to achieve various functionalities. The clock in an analog input/output circuit is used for providing a sampling or updating clock to an analog-to-digital converter or a digital-to-analog converter integrated circuit. And to use the clock signal in the digital input/output circuit is for digital signal sampling or renewing
The clock circuit is designed so as to allow selection of various frequencies by a user for enjoying or achieving various appliance features, or allowing to achieving various frequencies setup. Some methods of generating clock signal are described as follows.                (a) A time base clock signal generated from an oscillator is transmitted to a frequency divider circuit of a logic circuit to achieve various frequency setup. This method of setting up various frequency results in a poor frequency resolution, but however the manufacturing cost thereof is very low. Further, the functionality of the oscillation is limited to a certain range and is also of accuracy concern. For example, a time base clock signal frequency of 100 MHz, when divided by 2 results into 50 MHz; when divided by 3 results into 33.33 MHz; when divided by 4 results into 25 MHz; when divided by 5 results into 20 MHz; when divided by 6 results into 16.66 MHz, and so on, but however a frequency value between 50 MHz and 100 MHz, for example, a 75 MHz cannot be achieved by the above oscillator.        (b) A DDS (direct digital synthesizer) IC is capable of providing frequency adjustment with high resolution, wherein the adjustable frequency resolution to a degree of μ Hz, and therefore the resulting frequency can be very exquisite. The advantage of this method is the high frequency resolution, for example, are 211.354677 KHz, 301.3445 MHz and other fine adjustment range. But the disadvantage is the high manufacturing cost and the highly complicated manufacturing process for producing a DDS IC. Additionally, the vibration levels are related to the DDS IC.        (c) Use PLL (phase lock loop) technology to generate the clock signal. The PLL locks up the clock signal at a certain frequency and result in an absolute accuracy, however generally speaking, the clock resolution is poorer and the clock vibration levels are related to the PLL IC as well.        
The above three methods of generating clock signal have some advantages as well some disadvantages. If an user needs all the three types of clock generators, the user needs to purchase three measuring devices with different types of clock generators, and accordingly, the product management, the cost of design and the production would be expensive.
Therefore, a clock generator module suitable for applying in various circuit board and electronic products without incurring high cost is highly desirable.